Wheel chocks for restraining the movement of a motor vehicle in a carrier such as railroad cars are well known. An automobile may be held with wheel chocks in a container or cage, the floor of which is provided with a mounting rail, chock tie-down rail, or guide-rail, hereafter referred to as a “chock-rail”. Irrespective of how the automobile is to be transported, it is transported in a transportable carrier. More specifically, wheel chocks (hereafter, for brevity, “chocks”) such as are disclosed in U.S. Pat. Nos. 4,875,813; 5,037,255; and 5,316,421 (hereafter the “'813”, “'255” and “'421” patents, respectively) are currently in wide use to chock automobiles being transported; though these chocks may have bodies cast from a light metal alloy, typically an aluminum or magnesium alloy, or aluminum, they are currently molded from a synthetic resinous material (or “plastic” for brevity). The molded chocks are highly successful to chock most automobiles and pick-up trucks currently manufactured and transported in interstate commerce.
To date, the bodies of all '813 and '421 wheel chocks made and used in commerce have been molded from plastic, because it is more economical and practical to do so, it being understood that a metal body could be cast and used provided it meets the requirements of strength and stiffness with the maximum thickness stated hereafter. The reason the '813 and '421 chocks are unsuitable for a large number of passenger automobiles currently marketed is that, recently, these automobiles afford inadequate clearance for manually installing and removing the chocks in the front and rear wheel-wells (defined by the vehicle's front and rear fenders respectively).
In particular, the design and construction of the monolithic bodies of the chocks disclosed in the '813, '255 and '421 patents are highly desirable because these chocks allow the harness to be tightened and loosened on a torque tube which lies above a chock-rail to which the chock is secured. However, strength and stiffness considerations require that the elevational profiles of the molded bodies of the '813, '255 and '421 chocks be so high as to all but preclude manually installing each chock under a current “low-drag” automobile without damaging its adjacent body components. In addition to the confined space around the wheel of a “low drag” vehicle, making it difficult to deploy a wheel harness over the tire, and wheel chocks in front of and to the rear of a wheel, the height of the chock's molded body makes it difficult to chock a wheel without damaging wheel-well components which come in contact with either the chock body or the elongated restraining element (“strap” or “belt”) of its wheel harness under the dynamic conditions encountered while the vehicle is transported.
It is known that a current “low-drag” automobile can be adequately restrained if either the '421, '255 or the '813 chocks could be positioned against a wheel around which there is enough clearance above the chock to avoid damaging components of the automobile, but in many current automobiles this clearance is lacking. Damage to components of a fender well was caused not only by impact with the body of the wheel chock, but also by impact with the strap used to secure the wheel to the deck of the transporter. The difficulty lay in the redesign of the molded or cast body using a strap, so as to provide the desired clearances to avoid damaging components of the automobile when automobile is substantially static and when it is jolted during transport (dynamic conditions).
Since molding the body from an engineering plastic is more economical than casting it from metal, molding the body required configuring structural details so that they could be unitarily molded to have the required strength and stiffness within the limitations imposed by the process used to mold the chock's body from an engineering plastic of choice.
The Problem:
Automobiles are currently designed to coax maximum distance (mileage) out of a unit volume of fuel. The less the drag, the better the mileage. It has been found that reducing the clearance between the vehicle's wheel and body, the wheel well clearance, and/or reducing the ground clearance between the vehicle's body and ground reduces air turbulence and provides lower aerodynamic vehicle drag. The resulting “low-drag” design utilizes a body shape with fenders and rocker panels which are only 148 mm (5.82″), or even lower, above the ground on which the automobile rests. Therefore the novel chock was required to have a maximum height, at any cross-section, of 12.7 cm (5.0 ins), preferably no greater than 11.7 cm (4.6″), so as to fit under rocker panels, “ground-effects” components and stone guards of current low-drag designs and those reasonably foreseeable in the future.
In addition, the space around the tire of a wheel in a wheel-well is so restricted that it is difficult to manipulate a conventionally used '813 or '421 wheel harness which is to be hooked with straps to be wrapped around a torque tube in a wheel chock. The inner panels of the wheel-well are so close to the tread of a tire that the pending straps of a wheel harness used in combination with prior art wheel chocks, scuff and damage the inner panels. Such damage is exaggerated when a carrier is jolted and the vehicle suffers a dynamic shift resulting with a taut strap having an impact on an inner panel. The highly desirable use of a strap to secure a wheel to the deck with a wheel chock required that the damage attributable to the strap, when tightened, be minimized if not negated.
Though the interchangeability of each '813 or '421 chock is a desirable practical convenience, it decreed that rotation of the torque tube be in the same direction to tighten the straps. As a result, when the straps on each side of a wheel are taut, at least one strap is forced against an inner panel of the “low-drag” wheel-well under the slightest movement of the vehicle, resulting in damage to the panel. Major vehicle manufacturers have defined a three sided “safe zone” wherein the “chocking surface” and the strap and the point at which the strap is wrapped on the torque tube, must all be confined during static and dynamic loadings. The “chocking surface” is the angled surface against which the tire is biased when the strap is tightened. The sides of the safe zone are defined by (i) the arcuate surface of the tire tread from where it meets the deck up to the wheel's horizontal center line, (ii) a vertical plane from the tangent at the wheel's horizontal center line to the horizontal plane of the deck's surface and (iii) the deck surface intersecting the first two sides. The vertical plane defines the longitudinal limit of the safe zone specified by General Motors Corporation. The volume of the safe zone is directly proportional to the size of the wheel. Small wheels have small safe zones, large wheels have large safe zones.
There is a second zone, referred to as the “deck zone”, that is defined by a horizontal boundary plane not more than 2 inches (50.8 mm) above the deck surface upon which the wheel rests, and the deck surface, the plane extending fore and aft of the safe zone. The wheel chock is required to meet the requirements of the limits set forth in both the safe zone and the deck zone. Because of the tight confines of the safe zone, it was found essential that each strap, when tightened to secure the strap over a wheel, must be within the three sided safe zone when taut, so as to avoid scraping the inner panels. The safe zone is defined relative to the tire, so that when the tire is displaced dynamically (when the secured automobile is jolted), the safe zone is also displaced.
The high probability of such damage is not avoided by blocking the tires of a vehicle, typically by rolling the wheel onto a wood block about 45 mm (1.75 in) thick, raising the wheel's horizontal center line so as to increase the safe zone and to get adequate clearance above the deck floor, before securing the wheel in the wheel harness. With such a “quick-fix”, during transport of the vehicle, it is likely to be jolted with sufficient force to have the wood block ejected from under a wheel, resulting in damage. Therefore it was required that the novel chock not only be easily and reliably installed on a chock-rail, but also that the chock's molded body maximize the vertical and longitudinal clearance under dynamic conditions expected to be encountered during transport of the automobile.
Moreover, the '813 and '421 wheel harnesses required using a J-hook to secure the wheel. Manually manipulating each J-hook was found to be not only unexpectedly difficult in the tight confines of the wheel-well, but also likely to result in scratches to body components. When two “active” wheel chocks are to be used, a hookless wheel harness was required. By “active” wheel chock is meant one with a ratchet gear assembly used to tighten a strap wound around the chock's torque tube. By “hookless harness” is meant a harness which does not require assembly with hooks. In particular, a multicomponent harness requiring J-hooks, or some other metal fastening means to assemble portions of the harness after one or more of the portions was deployed over the wheel, was specifically proscribed. When a single active wheel chock is to be used in combination with an anchor wheel chock, a hook or other tube engaging and securing means is required to secure one end of the strap to an anchoring element in the anchor chock. A rod, strut or tube in the anchor chock provides a convenient anchoring element. To distinguish the rod, strut or tube used as an anchoring element in an anchor chock from the torque tube used in an active chock (because the torque tube may be used as the anchoring element), the anchoring element is referred to hereafter as a rod, though it will be appreciated that a tube would be preferred.
Since desirable features of the '813 and '421 chocks, namely their operability from outside the chock-rail, by an installer facing one side of the automobile, of both the wheel-securing ratchetable torque tube (harness-tightening and loosening mechanism to tighten and loosen the ends of a harness strap) and the locking mechanism (to lock the chock to the rail), proved to be exceptionally effective, it was decreed that a molded or cast body be configured to house these features in an active chock. Since the torque tube in the prior art chocks lay above the chock-rail, a new design mandated that this position of the torque tube be retained. The active wheel chocks and anchor chock are required to be installed on any chosen “standard” chock tie-down rail; the standard in the U.S. is set by the AAR (American Association of Railroads).
Still further, since a practical wheel chock mandates a molded plastic body or a cast aluminum or light alloy body, to avoid damage to a vehicle's body components, it is necessary to construct a monolithic body with thin stiffening ribs or webs. Any peripheral wall of the body, or any internal stiffening rib or web thicker than 15.9 mm (0.625 in) thick cannot currently be either reliably or reproducibly injection-molded from an engineering plastic or cast from a light metal. Further, because any external stiffening rib, projecting outwardly from the smooth exterior surfaces of the chock's body, will add to the critical external dimensions of the wheel chock and increase the likelihood of damage caused by the projecting rib, it is essential that no such external stiffening rib be used in a low profile chock.